The present invention disclosed herein relates to an apparatus for monitoring a process, and more particularly, to an apparatus for monitoring a gas, which detects fluorescence of an exhausted product gas and plasma process equipment including the same.
In general, silicon and silicon compounds are the most important material in solar cell and semiconductor fields. The silicon and silicon compounds are used for various purposes such as the formation of a semiconductor thin film, an insulator film, a protective film, and a buffer layer. A silicon thin film and silicon compound thin film may be formed on a substrate by mainly using vacuum deposition equipment. The vacuum deposition equipment may be polluted and unintentional deposits may be accumulated on the wall in proportion to usage time. Accordingly, the vacuum deposition equipment requires time-consuming dry-cleaning process every predetermined cumulative time.
A dry cleaning is a method of cleaning the inside of a chamber of the vacuum deposition equipment through plasma reaction. For example, a dry cleaning process gas of a chamber in which a thin film such as Si, SiO2, Si3N4, and SiC is deposited may include fluoride compounds such as SF6, CF4, C2F6, and NF3 which have excellent etching characteristics. However, since the fluoride compounds are greenhouse gases accelerating global warming, their emission has to be restricted. In addition, since the fluoride compounds are relatively expensive, cleaning costs may increase when a large amount of cleaning gas is used.
A method of measuring a cleaning endpoint may efficiently prevent or reduce economic and environmental losses by reducing excess consumption of cleaning gases. The cleaning endpoint of the dry cleaning process may be measured by a surface reflectance of a solid specimen, an etch stop layer, or an optical emission spectroscopy (OES). The OES may provide information concerning the cleaning endpoint through a spectrum change of species in plasma during cleaning process. In recent years, plasma process equipment that monitors the behavior of light emitted from a species in plasma to detect the cleaning endpoint has been suggested. However, an endpoint detection error may occur by interference in the plasma reaction. Furthermore, OES spectra are highly complicated, and thus expensive equipment such as a monochromater is required for exactly measuring a pattern for each wavelength to detect the endpoint.